1. Field of the Invention
The control of friction and wear under high load conditions requires boundary lubrication. Boundary lubrication appears to depend on the properties of the lubricant other than its viscosity. Boundary lubrication can be achieved by the formation of films on the metallic surface. While the formation of such film is thermodynamically favored, the thickness of the surface film ranges from a few-hundredths of a microinch for single molecule layers of adsorbed gases to several dozen microinches for thick films from oils with extreme pressure (EP) additives. A problem in the lubrication art is to provide a boundary film with the proper chemical and physical characteristics to control friction and/or wear under high load conditions, and the correct chemical properties to avoid detrimental damage to the surface and other disadvantageous effects such as toxicity, oxidation catalysis and sludge deposition.
It is important for many applications that the lubricating compositions give a minimum value of 60 pounds in the Timken Extreme Pressure Test (ASTM D2782-71). A 60-pound minimum requirement is ordinarily set by the U.S. steel industry and by other industrial users of extreme pressure gear oils. The novel combination additives of the present invention provide lubricants which easily exceed this requirement, and, in fact, the preferred ternary combinations provide EP values in the Timken test as high as any EP additives known. They also produce compositions of excellent stability, and low wear.